Automatic firearm breechblock stop



July 3.8, 1944. WEBB AUTOMATIC FIREARM BREECH BLOCK sToP T?Vsn or jauge Webb Filed April 6, 1942 Patented July 18, 1944 UNlTED S'l" QFFMIE AUTOMATIC FIREARM BREECHBLOCK STOP Application April 6, 1942, Serial No. 437,852

6 Claims.

This invention relates to a breech block stop for an automatic firearm. The invention is particularly applicable to automatic rearms of the caliber 37 mm. automatic cannon type, but its application is not restricted to guns of this type since the principles of the invention may be applied to guns having diierent calibers and of different constructions wherein breech block stops of the type disclosed herein may be utilized.

The breech block stop disclosed in this application comprises improvements over those disclosed in U. S. Patent 1,525,065 to Browning, U. S. Patent 2,297,640 to Webb, and cl3-pending application, Serial No. 325,405, filed March 22, i940.

It is an object of the present invention to provide a breech block stop which is horizontally movable forward. to remove the stop from its normal position for stopping or arresting the downward movement of the breech block when it is desired to completely remove the breech block from the firearm.

It is another object of the invention to provide a spring for biasing the breech block stop to its normal position in which it is adapted to stop the downward. movement of the breech block and hold the breech block in its normally lowermost position.

A further object of the invention is to provide positioning means on the breech block stop adapted to cooperate with a slot or recess in the bottom of the breech block to prevent horizontal movement of the lower end of the breech block in a direction transverse to the axis of the rearm.

Other details and objects of the invention will become apparent from considering the following specification.

` The accompanying drawing shows the embodiment of the invention which is deemed preferable, but it will be understood that the drawing is intended for illustrative purposes only and is not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

In the drawing,

Fig. 1l is a fragmentary side elevation of an automatic firearm in which a breech block stop comprising the present invention is shown in its ,normal position and the breech block is in its breeched position.

Fig. 2 is a fragmentary vertical sectional view taken along the line 2-2 of Fig. 1 but showing the breech block in its' normally lowermost position and omitting certain parts of the rearm.

Fig. 3 is a fragmentary vertical sectional View taken along the line 3-3 of Fig. 1.

Fig. 4 is a fragmentary side elevation of the breech block stop shown in Fig. l, this elevation being partly in section along the line 4--4 of Fig., 3, the breech block being in its normally lowermost position.

Fig. 5 is a fragmentary side elevation similar to Fig. 4 but showing the breech block stop retracted and the breech block partially removed from the firearm.

The automatic firearm, hereinafter referred to asA a gun, to which the present invention is applicable is of the type illustrated in complete detail in said co-pending application, Serial No. 325,405, and said gun is also similar to the type illustrated in said Browning Patent 1,525,065. inasmuch as the present invention deals with the construction of the breech block stop, only sutcient details of the entire gun are herein described and illustrated to form a basis for understanding the characteristics of the details and functions of the breech block stop. For an illustration and description of the entire gun, attention isinvited to said above-mentioned patent and application.`

Guns of the type to which the present invention is applicable are well adapted for use in airplanes, although their use is not so limited. Such guns are normally mounted in various predetermined positions in airplanes and, especially during combat, the airplane and gun will assume a great many dilerent positions while the airplane is being maneuvered. It is essential that the gun be able to re while in any of these positions. However, the mounting means for the breech block of guns of this type is such that after the operating lever has moved the breech block to open position away from the breech of the barrel, the operating lever disengages from the breech block, whereby the breech block is free to move in its guideways under the force of gravity.

To control the movement of the breech block after such release, stop means have been provided to limit the movement of the breech block away from the breech end of the barrel. Said stop means are attached to the gun by suitable mounting structure whereby the stop may be readily retracted from the path of movement oi' the breech block to permit the breech block' to move past the stop and thus be entirely removed from the gun. Furthermore, it has been found that under certain situations occurring during maneuvering of an airplane, such as when banking, if the breech block is in its lowermost position and resting on the stop, centrifugal force will tend to throw the lower end of the breech block to one side of its normal position in which it is normally engaged by the operating lever whereby, when the operating lever is moved forward to engage in the slot in the lower end of the breech block, the slot will not be in proper `alignment to receive the operating lever and a misfunction of the gun results.l To prevent the occurrence of such misfunctions due to this cause,

actuating lever for raising and lowering the breech block as will be presently explained.

y Longitudinally movable within the breech casing is a lock frame 26, the upper portion of which is of such width as to permit it to move between the arms la of the barrel extension. Depending from the lock frame 26 is a yoke 28 to which are detachably connected two transversely spaced tension-rods 29.

means are provided in the present invention to maintain the lower end of ,the breech, block The depending lug |8 ofthe barrel extension supports a yoke 3i! by means of a channel 3|)c which is formed in the lower` face of the lug to provide a mounting seat for a projection 36d exby rivets y39?, or any other suitable connecting provides suitable mechanism forcontrolling the movement of the breech block inall conceivable positions of operation of the gun, whereby ther breech block will function properly in all such positions of the gun. l

Referring to thedrawing, the gun is shown dis.

posed horizontally withv its sides influpright position. With respect-hto-Fig. ALuthe forward ror barrel end of the gun is toward the right while therear end of the gunis'towardthe left. .This position of the gun might be consideredthe normal position.' -All `relative terms hereinafterV used, such as downwardV .upward,-horizon tal, verticalj forward rearward vand the like are to be considered relative to the normal position referred to.

The breech casing 2-houses most of the operating and movable elements of the gun. LA trunnionblock 3 is provided inthe Yforward end of the breech casing. Projecting from the forward endof the breech casing-land slidably disposed in thetrunnion block" 3 is a barrel 4-provided at its breech end with threads-4a. vvAlso slidably disposed within the-breech casing-is 'a barrel -eX- g tension I8. Theiorwardv body portion of the barrel extension is apertured and threaded to receive the threaded breech end of the barrel or 'tube and detachably lretain the barrelin operacts through a recuperator rodl 22 which is connected at itsrearend with the depending lug I8c on the barrel extension' I8. A nut *22a threaded on the rod serves to `eilect connection of the re cuperator rod with the lug '|8c.

Carried by the barrel extension I8 is a breech block 25 which is arranged to slide substantially vertically between the parallel arms |89; of'tlfle barrel extension; 'The block is guided in its yvertical movement bya pair' of ribs 25a whichare respectively disposed "on opposite 'sides `of, the breech block to lit corresponding grooves formed in the arms I8aof the barrel extension. In Fig. 1, the breech block .is shown in its ,uppermost breech-closing or breeched. position; The lower portion of the breech block 25v has a rearward projection 25b and in this longitudinally widened lower portion of the, breech block, there is pro-,- 'vided a T-slot or recess 2,15? which receives the means,V whereby the yoke and lug cooperate as a substantially integral unit and for purposes of simplifying the explanation of the invention, the yoke and lug may be considered a unitary member asv far as the'mountingof the slidable stop member, to bepresently described,.is concerned. The yoke is provided with projecting arms 36a, 3|)a as .shown particularly Yin Fig..3. n Detachably supported in part onthe arms a, 36a arertubes 3|, 3| which receive .the tension rods 29, 29 and also receive reaction or driving springs 32 surrounding the tension rods.. ,The springs 32 abut at their rear ends againstplugs 3|2L in vthe vrear ends of the tubes 3|, and abut at their forward ends against'collars (not shown) on the rods29, 29 near the vforward ends thereof-, J

Pivotally mounted between downward projecting lugs 276a on kthe lock frame, isa breech block actuating or operating lever 33. For purposes of explaining the operation of the mechanism comprising the mainpart of. this invention, itis sufcient to briey state that the operating lever is provided with suitable laterally vprojecting lugsor studs 33C, ,33"1 and 33e. -Said lugs each yproject from opposite sides of the operatinglever and the oppositely disposed portions of the:lug';33 are adapted to engage in the T-shaped slot 25c of the breech block for raisingand lowering the breech block `as ,the operating leveris moved about its pivot during the-operation Aof the gun. Movement of the operating lever 33 is controlled and guided by the studs ,33dland,33jco-actingwith cam surface 35, cani` groove 35?*.and other cams and groovesk (not shown) provided on the VV.rire- Y arm. Said studs and "cams are broughtinto en,-

gagement with each other: throughrthe Inovementof the lock frame 26 which carries the op,- erating lever 33 therewith. D y I l With .the above-described parts of Athe iirearm in the position shown in Fig. 1, when'theiring ofy a cartridge orround takesv place, they barrel and barrel extension.move'rearwardiagainst the force of recuperatorfspringj.20.` "Ifhe' lock frame 26, together with yoke'28 and operating lever 3,3,

l also moves rearward againstntheforce of springs 32.*v In vso moving, jlugs '33i of ',operating'lever S3 engage cam surfaces 35,170 move the' forward end of the operating lever downward and, in so moving, the lugs 33, which arey disposed inf \T shaped slot 25c of the breech block;move'V the breech block 25 downward while'the lock frame and operating lever meanwhile continue tomove rearward. VDuring vthefcourse of such rearward movement ofthe operating fleve'fr, the lugs 3l!`c will be withdrawn from the rearward'end of the slot'c to lthus entirely disconnectthe operating lever from the breech block. The breech block; due to momentum yofjitsinitial movement, continues to move downward 'and,. unless otherwise opposed, would move completely from the lower end of the guideways in the barrel extension and drop from the gun.

To prevent such complete removal of the breech block during normal operation of the gun, downward movement of the breech block is normally limited or arrested by a stop which is in some respects similar to those disclosed in my previously mentioned Patent 2,297,640 and in Browning Patent 1,525,065. The constructio-n shown herein differs, however, from the construction shown in said application and patent and has certain advantages thereover.

The yoke is provided with a rearward projecting ledge or aligning means 39. Supported on the ledge and slidable thereon isa/stop member 4D which is provided on its forward face with a cylindrical portion or guide member L'id. The rearward face of the stop is provided with a stop portion A@Ilc which is adapted to directly engage the bottom of the breech block to limit downward movement thereof. The unitary projecting lug ISC and yoke 30 are provided with a transversely extending hole or opening which is preferably counterbored from one end to provide a cylindrical bearing clla which has an annular seat at its innermost end. The guide member llild of the sto-p is slidably disposed in the open end of the counterbored portion die.

A guide shaft we extends through the opening in the lug and yoke and is threadably connected at its rearward end to the stop ll. Said end of the shaft is also reduced in diameter and the reduced portion is formed with an annular groove 40e. Suitable aperture formed in the stop in alignment with the underside of the annular groove fiile, whereby said pin locks the shaft and stop in threaded assembly.

A helical spring 6l surrounds the shaft 46a and the rearward end of the spring abuts against the inner `end of the member dlld and the other or forward end of the spring abuts against the annular seat on the interior of the counterbored portion fila. The spring 6il serves to normally bias the stop toward its rearmost position in which the stop portion du is adapted to engage the bottom of the breech block to limit downward movement thereof. By this arrangement it will be seen that the spring is completely enclosed within the interior of the lug I8c whereby the spring will be maintained relatively free from the accumulation of dirt and other extraneous material which might otherwise collect in the counterbored portion llla if the opening were not closed at both its ends.

To insure that the stop will not move rearward past the proper rearmost position, the outer end ofthe shaft 40@ is provided with an enlarged head 4tlg which forms a stop means to limit or arrest the rearward movement of the` stop. Preferably, the lug ISG is provided with a suitably shaped counterbored recess lh'to receive the head deg when the stop is disposed in the position shown in Fig. 4.

After the breech block has reached its normally lowermost position and is at rest on the stop 40, said stop is maintained in such position against accidentalk or unintentional upward movement by a spring-pressed slidably mounted detent 42 which is carried by one arm l8r of the barrel extension, as shown in Fig. 2. The detent is l0- cated on the arm in proper position to engage the upper end of the breech block when the breech block is in said lowermost position. De-

A locking pin def is inserted in a tails of the spring-pressed detent are set forth in a co-pending application, Serial No. 314,272, filed January 17, 1940, in the name of William L. Swartz, now Patent 2,339,661 dated January 18, 1944. The strength of the spring normally urging the detent 42 inward is such that it will cause the detent to maintain the breech block in its lowermost position but, when the breech block is engaged by the operating lever 33 for upward movement to breeched position, the spring will readily yield to permit the breech block to cam the detent to inoperative position.

When it is desired to remove the breech block from the gun for inspection, cleaning, or replacement, this can be readily done by manually moving the stop member 49 forward to its inoperative position shown in Fig. 5. The breech block will then move downward by gravity, past the stop 4), as shown in said gure. When the breech block is to be replaced, it is press-ed against the stop member 40 so as to force it forward and then the breech block can be pushed upward into its normally lowermost position, the stop member being pushed rearward by the spring lll to cause the stop portion 40C to snap under the blo-ck and retain it in that position.

When the breech block is in its normally lowermost position, as shown in Fig. 2, only the upper portion of the breech block is between the guide grooves in the arms 18a of the barrel extension. The major portion of the breech block is below the guide grooves and inasmuch as a small amount of clearance is normally allowed between the guide ribs 25a on the breech block and the grooves in the barrel extension arms, a certain amount of horizontal movement of the lower end of the breech block may take place in both transverse and longitudinal directions with respect to the gun. Of these two movements, movement of said end of the breech block transversely of the gun is apt to cause a misfunction of the iirearm if such movement is sucient that the studs 33a of the operating lever will not properly align with the upper horizontal portion of the T-shaped slot 25 in the lower end of the breech block. Such horizontal transverse movement of the lower end of the breech block may be produced, for example, when the gun is mounted in an airplane and the airplane is banking in a turn. Under these conditions, the lower end of the breech block will be moved, due to centrifugal force, in a horizontal transverse direction and if such movement is appreciable,one of the lugs 33C will abut the rear face of the rearward projection 25b rather than both of the lugs entering the slot 25C.

To prevent the foregoing misfunction from occurring, the breech block stop is provided with a projection 45h which, in the preferred embodiment, is formed integrally with the stop and projects upward from the stop portion 138 a dis-- tance approximately equal to half of the length of the vertical portion of the T-slot 25C, as clearly shown in Fig. 2. Preferably, the base of the projection 4Gb is as Wide as the lower portion of the T-slot and the sides of the projection respectively taper inward toward the top whereby, when the breech block is moving downward toward its lowermost position against the stop portion 40, if the T-slot is not exactly in its proper position to become seated on the projection, the bevelled sides thereof will cause the lower end of the breech block to be cammed into its proper transverse position on the stop.

Inasmuch as the breech block is held in said lowermost position by the detent 42, engagement ofthe projectionb with the T-slot will be maintained and the `projection will insure the (proper positioning of the lower end of the breech block whereby the T-slot will receive the lug 33 of the operating lever when the breech iblock is to be raised by saidoperating lever` during the functioning of the gun. Consequently, misfunctioning of` the vgun due to, improper positioning of the T-slot for reception of the lugs 33 is prevented. It will be understood, of course, that the invention is not restricted to the exact size and shape of the projection shown in the preferred embodiment. Furthermore, inasmuch as the projection extends rearward no farther than the stop portion the projection will in'no way interfere with the release of the breech block when the stop is moved forward to the position shown in Fig. 5. Y Y

From Figs. 3`and 4, it will be observed that rotation of the nut 22 on the end of the recuperator rod 22 is prevented'as long as the stop 4G is in the position shown in these figures. The stop, therefore, serves a |plural purpose of not only limiting the movement of the breech block, but also preventing rotation of said nut. However, when the stop is moved to the position shown in Fig. 5, the nut may be rotatedy if desired.

It will thus be seen that the breech block stop described above affords means for limiting the downward movement of av breech block after the operating lever has been vdisconnectedtherefrom during the normal operation of the gun. The stop is of simple and efficient construction and is adapted for expeditiousv manual manipulation requiring the use of no tools or mechanism of any kind. Not only does the stop provide means to arrest the downward movement of the breech Iblock and maintain it in its lowermost position when the stop is in its normal operating position but the stolp simultaneously provides means to normally prevent rotation of thenut which secures the recuperator rod to the barrel extension. Furthermore the Ystop includes means to prevent horizontal movement of the lower end of the breech block in a direction transverse to the axis of the gun. Inaddition, the stop may be manually moved forward to inoperative posi-` tion against the action of its biasing spring whereby the breech :block may be completely removed from the underside of the gun.

While the invention has been illustrated and described in its preferred `embodiment and has included certain details, Vit should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways,l

falling within the scope ofthe invention as upward in timed relation with the reciiprocationA of the barrel and barrel extension, in combination with a stop member carried by the vbarrel extension and having a portion positioned to limit downward movement of the breech block,

one of said members being formed with a recess and the other member having a projection adapted to be received Ain said recess when the breech block vmember is in engagement with said stop member lto member in a direction transverse tothe horizontal vaxis of the firearm. Y l

2. An automatic firearm comprising in co-mbination, a casing, a longitudinally, reciprocable barrel having a barrel extension connected therewith and positioned within the casing, a breech block guided on the barrel extension-for downward and upward movement out of and into breech-closing position, said breech block having a recess formed in the lower end 'thereon' and mechanism for moving the breech block downward and upward in timed relation withtheV reciprolcation of the barrel'and barrel extensio-n, in combination with a stop carried by the barrel extension and having a portion positioned to limit downward movement of the breech block, and a :projection on said stop adapted to engage said breech block recess when the breechblock is in engagement with said stop, whereby horizontal movement of the lower end of the breech block in one direction is substantially prevented.

3. An automatic iirearm comprising in combination, a casing, a longitudinally reciprocable barrel having a barrel extension connected therewith and positioned within the casing, a breech block guided on the barrel extension for downward and 4upward movement out of and into breech-closing position, said breech block having a recess formed in the lower end thereof, and mechanism for moving thebreech blockV downward and upward in timed relation with the reciprocation of the barrel and barrel extension,

` said mechanism including a member adapted to engage said recess while moving said breech block upward and downward, in combination with a stop carried by the barrel extension and having a portion positioned to limit downward movement of the breech block, and a projection on said stop adapted to engage said breech block recess when the breech block is in engagement with said stop, whereby horizontal movement of the lower end of the breechblock in a direction transverse to the firearm is substantially prevented.

4. An automatic Viirearm comprising in combination, a casing, a longitudinally recprocable barrel having a barrel extension connected therewith and positioned within the casing,l a breech ,i block guided on the barrel extension for downward and upward movement out of and into breech-closing position, said breech block having a recess formed in the lower end thereof, and mechanism for movingthe breech block downward and upward in .timed relation with the reciprocation of the barrel and barrel extension, in combination witha stop carried by the barrel extension and positioned to limit downward movement of the breech block, and a projection having opposite sides tapering inwardy toward the f substantially prevented.'

5. An automatic firearm comprising in combination a casing, a longitudinally reciprocable barrel having a barrel extension connected therewith and positioned withinthe casing, a breech substantially prevent horizontal l movement of the lower end of the breech block,

block guided on the barrel extension for downward and upward movement out of and into breech-closing position, said breech block having a recess formed in the lower end thereof, and mechanism for moving the breech block downward and upward in timed relation with the reciprocation of the barrel and barrel extension, in combination with a relatively movable stop carried by the barrel extension and normally in a position to limit downward movementl of the breech block, the said stop also being normally freely movable substantially horizontally in a direction to release the breech block, and a projection on said stop adapted to engage said breech block recess when the breech block is in engagement with said stop, whereby horizontal movement of the lower end of the breech block in a direction transverse to the firearm is substantially prevented.

6. An automatic firearm comprising in combination, a casing, a longitudinally reciprocable barrel having a barrel extension connected therewith and positioned within the casing, said barrel extension being provided with an opening Til forming a guideway, a breech block guided on the barrel extension for downward and upward movement out of and into breech-closing position, said breech block having a recess formed in the lower end thereof, and mechanism for moving the breech block downward and upward in timed relation with the reciprocation of the barrel and barrel extension, in combination with a relatively movable stop carried by the barrel extension and normally in position to limit downward movement of the breech block, the said stop also being normally freely movable horizontally in a direction to release the breech block, a member formed on said stop and slidably disposed in said guideway for guiding the movement of said stop, a projection on said stop adapted to engage said breech block recess when the breech block is in engagement with said stop to prevent horizontal movement of the lower end of the breech block in a direction transverse to the firearm, and a spring disposed in said guideway and abutting the inner end of said member on said stop to bias the stop for movement to its normal position.

GEORGE WEBB. 

